/**
 * Copyright 2009-2017 the original author or authors.
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.ibatis.parsing;

/**
 * @author Clinton Begin
 */
public class GenericTokenParser {

	private final String openToken;

	private final String closeToken;

	private final TokenHandler handler;

	public GenericTokenParser(String openToken, String closeToken, TokenHandler handler) {
		this.openToken = openToken;
		this.closeToken = closeToken;
		this.handler = handler;
	}

	public String parse(String text) {
		if (text == null || text.isEmpty()) {
			return "";
		}
		// 获取第一个openToken在SQL中的位置
		int start = text.indexOf(openToken, 0);
		// start为-1说明SQL中不存在任何参数占位符
		if (start == -1) {
			return text;
		}
		// 將SQL转换为char数组
		char[] src = text.toCharArray();
		// offset用于记录已解析的#{或者}的偏移量，避免重复解析
		int offset = 0;
		final StringBuilder builder = new StringBuilder();
		// expression为参数占位符中的内容
		StringBuilder expression = null;
		// 遍历获取所有参数占位符的内容，然后调用TokenHandler的handleToken（）方法替换参数占位符
		while (start > -1) {
			if (start > 0 && src[start - 1] == '\\') {
				// this open token is escaped. remove the backslash and continue.
				builder.append(src, offset, start - offset - 1).append(openToken);
				offset = start + openToken.length();
			} else {
				// found open token. let's search close token.
				if (expression == null) {
					expression = new StringBuilder();
				} else {
					expression.setLength(0);
				}
				builder.append(src, offset, start - offset);
				offset = start + openToken.length();
				int end = text.indexOf(closeToken, offset);
				while (end > -1) {
					if (end > offset && src[end - 1] == '\\') {
						// this close token is escaped. remove the backslash and continue.
						expression.append(src, offset, end - offset - 1).append(closeToken);
						offset = end + closeToken.length();
						end = text.indexOf(closeToken, offset);
					} else {
						expression.append(src, offset, end - offset);
						offset = end + closeToken.length();
						break;
					}
				}
				if (end == -1) {
					// close token was not found.
					builder.append(src, start, src.length - start);
					offset = src.length;
				} else {
					// 调用TokenHandler的handleToken（）方法替换参数占位符
					builder.append(handler.handleToken(expression.toString()));
					offset = end + closeToken.length();
				}
			}
			start = text.indexOf(openToken, offset);
		}
		if (offset < src.length) {
			builder.append(src, offset, src.length - offset);
		}

		return builder.toString();
	}

	public static void main(String[] args) {
		String text = "${";
		int start = text.indexOf("${", 0);
	}
}
